Chlorine vs Chloride of Lime

simple axiomatic truth seems to have been overlooked by those who try to use chlorine instead of chloride of lime, and thus bring about endless complications, due to chlorination on account of the direct action of chlorine on organic bodies. From solutions of hypochlorites, carbonic acid contained in the air, or in water, or other dilute or weak acids, will liberate free hypochlorous acid; the latter in the active oxidizing agent of chloride of lime. Although it is such a weak acid that almost all other acids, however weak, may drive it out of chloride of lime, it is probably the most powerful oxi- dizing agent known to chemists. It will give up nascent oxygen with extreme readiness: 2 HOCl=2HCI+20, and therefore, when liberated in dilute solutions of chloride of lime by the minute quantities of carbonic acid ever present in water and air, it only can oxidize gradually, or as it were, in sections, the measure for each section being the carbonic acid temporarily available; this may explain why hypochlorites are the least wasteful oxidizing agents as well as in their “selective action” on organic bodies and bacteria, the less resistant ones making first claim on the ever limited amounts of nascent oxygen. When free hypochlorous acid is brought in contact with hydro- chloric (muriatic) acid, the constituents of both become promptly resolved into water and chlorine: HCIO+HCI=H,0+2 Cl. For this reason, hydrochloric acid by itself, or such strong 8 Chloride of Lime in Sanitation. acids as would evolve hydrochloric acid from the ever-present calcium chloride, must be avoided and weaker acids (acetic) are used in the arts for setting free hypochlorous acid in solutions of chloride of lime. Chloride of lime is valued and sold on its percentage of “ avail- able chlorine,” a term which indicates the whole amount of free chlorine that becomes available in decomposing chloride of lime by means of strong acid. From preceding remarks, it must become clear that “available chlorine” is derived, Half from the calcium hypochlorite, and Half from hydrochloric acid employed either as such or gen- erated from the calcium chloride through action of another strong acid. In keeping and storing chloride of lime, the factors to guard against are carbonic acid, moisture, light and heat. Therefore it should be kept in closed vessels, and in a dry, cool place. The total amount of available chlorine has been found to be diminished: In very hot seasons by 1% per month. In winter by 1-3% per month. Composition of chloride of lime: Lunge (Sulphuric Acid and Alkali, Vol. 3, p. 642) gives two typical analyses of commercial chloride of lime which may be of interest as follows: Available Chlorine 37.00% 38.30% Chlorine as Chlorides . 0.35 0.59 Chlorine as Chlorates 0.25 0.08 Lime... 44.49 43.34 Tron Oxide 0.05 0.04 Magnesia. 0.40 0.31 Alumina. . 0.43 0.41 Carbon dioxide . 0.18 0.31 Silica, ete... 0.40 0.30 Water and loss 16.45 16.33 | | 8 8 : 8 Chloride of Lime. 9 From this we might assume the constitution of commercial bleach to be 4Ca0Ch, 2Ca(OH)s, 5H:0 analyzing 45.1 % Lime (CaO) 16.85 Water (H,0) 38.05 Chlorine (Cl) 100.00 or 68.0% Calcium Hypochlorite (CaOCk) 20.0 Calcium Hydroxide (Ca(OH).) 12.0 Water (H,0) 100.00 How to dissolve chloride of lime: It has already been stated that calcium hypochlorite (CaOCh) is the active bleaching and sterilizing constitutent of chloride of lime, splitting up in the presence of organic substances into nascent or active oxygen and calcium chloride (CaCh). The carbonic acid dissolved in the water releases free hypochlorous acid (HOCI) which acts similarly as a powerful oxidizer as well as a specific poison for many pathogenic bacteria. The excess of calcium hydroxide of lime which is present is not so readily soluble, and to this is largely attributable the sludge or milky solution produced. The point of particular interest in obtaining clear solutions of chloride of lime for a constant feed in water or sewage puri- fication, as well as in bleaching, is that the available chlorine or hypochlorite is quite easily soluble, even in fairly cold water, and the undissolved sludge of hydrated lime, silica, etc., settles readily. At least, settling takes place readily if a few simple rules are observed: First, do not mix too stiff a paste, otherwise a gelatinizing action takes place and greater difficulty in settling is encountered. Never mix a paste with less than one-half gallon of water for one pound of chloride of lime. Second, it is not necessary or desirable to grind or break up the lumps too thoroughly; the available chlorine nearly all dis- 10 Chloride of Lime in Sanitation. solves readily and too much agitation is detrimental to prompt settling. With these points in mind, we can now consider the prepara- tion of a stock solution of chloride of lime containing approxi- mately 2% of available chlorine. Three hundred pounds of commercial chloride of lime (85% available chlorine) equals 105 lbs. of available chlorine, assuming recovery of 100 lbs. of this free from sludge. These 100 lbs. must be contained in 600 gallons to give a clear 2% standard solution. Due allowance must be made for proper washing of the sludge, it thus contains in addition to the suspended lime and silica, a solution of equal strength to that of the clear liquid. The amount of sludge is equivalent to about 1 gallon for each 5 Ibs. of chloride of lime used. Economical working makes it desirable to use two tanks, each equipped with agitators and preferably a looped chain as a drag along the bottom. These tanks should be made of concrete, or at least lined with cement, and adjustable means provided for drawing off the clear liquor from above, as well as an outlet for removing the sludge at the bottom. Assuming that two 700-gallon tanks are provided, and that 300 Ibs. of chloride of lime giving 600 gallons of clear 2% solution are to be prepared in each tank at one mixing, the procedure should be as follows: . Into tank No. 1, which is empty, is drawn 200 gallons of weak wash water from tank No, 2. Then 300 lbs. of chloride of lime is dumped into the tank and mixed for one-half hour. The tank is now filled to a mark indicating 660 gallons with the remaining wash water from tank No. 2, which does not have to be particularly clear. This is now allowed to settle for at least 8 hours and preferably over night. There is ready to draw off to the stock tank 600 gallons of clear solution. There will remain about 60 gallons of sludge which requires washing to obtain the remaining available chlorine. The agitator is now started and the tank filled to the 660-gal- lon mark with water, and then allowed to settle. Chloride of Lime. ll This wash water is used in making up the next batch in No. 2 tank; the now practically exhausted lime sludge is thrown away. The standard stock solution thus prepared will contain avail- able chlorine equal to 3 Ib. of chloride of lime per gallon, or about 2% available chlorine or 6% of chloride of lime by weight. Hence an average filtered water requiring 8 Ibs. of chloride of lime per million gallons will require 16 gallons of this standard solution per million gallons of water. This is a trifle less than 1 drop of this solution containing 2% of available chlorine in a gallon of water. The following table covers the range of chloride of lime ordi- narily used in water purification, and may be found useful for comparison: aa) di i fg | ay | agss 3 SE Stee te nr re ea By] de | Hy] a | by deg ahs | ERE | g3e gi | git | facade 2 24 08 104 005 25 4 48 16 -028 -009 50 6 .72 24 042 -014 115 8 +96 82 -056 -019 1.00 10 1.20 -40 -070 -023 1.25 12 1.44 48 084 -028 1.50 14 1.68 56 -098 033 1.75 16 1.92 64 112 037 2.00 18 2.16 72 .126 042 2.25 20 2.40 80 .140 047 2.50 22 2.64 -88 154 -051 2.75 24 2.88 96 168 056 3.00 26 3.12 1.04 182 -061 3.25 28 3.36 1.12 196 065 3.50 30 3.60 1.20 210 070 3.75 12 Chloride of Lime in Sanitation. CHLORIDE OF LIME FOR WATER PURIFICATION. OSSIBLY nothing appeals more to the ssthetic taste than the thought of cool, sparkling water, fresh from some mountain or hillside spring. Nothing is more vital to the health, the vigor, the productive- ness of a community than pure water, and nothing is more readily within our reach if we will but insist upon it. The ancient Romans recognized this when they built the viaducts to the far-off hills and mountains for their water supply. We do the same in many cases today, and yet with an ever- increasing population the problems of obtaining an adequate and unpolluted water supply is becoming daily more difficult. Water we have, and plenty of it, but what do we do to preserve and protect it? Our streams and lakes are converted into sewers and catch basins, and then we ask our neighbors down the stream to drink this God-given water which we have poisoned with a myriad germs of typhoid and other intestinal diseases or worse. This speaks but ill for our much vaunted civilization, and yet this very civilization has given us the means of correcting this evil; furthermore, the fact that we live in cities makes possible 8 unity of action and scientific control of our water supply which is difficult if not impossible in rural communities. It is not too much to say that today any city with a popula- tion of 50,000 can have a better and more wholesome water supply than is possible in any rural community. But woe betide the city that does not take care of its water supply: the conse- quences are epidemics—wholesale murder—nothing less. A case of typhoid fever due to a polluted water supply should be as good ground for legal redress and recovery of damages as a broken limb due to a defective sidewalk. The direct interdependence between polluted drinking water and the typhoid death rates have earned for the latter the term “Index of Municipal Sanitation.” Recent investigations show that the results of water pollution are even more far-reaching than was generally supposed, Chloride of Lime for Water Purification. 13 Prof. Charles Gilman Hyde of the University of California brings this out admirably." He speaks of the so-called Hazen Theorem as follows: “Messrs. Mills (1893), Reincke (1893), Hazen (1904), Sedg- wick (1910), and others have shown that when a pure water supply has replaced an impure one in a community, the general death rate therein is generally reduced in a considerably greater degree than would be accounted for by the reduced prevalence of Typhoid Fever and other recognized typical water-borne diseases. A study of the vital statistics of numerous places where the quality: of the public water supply has suddenly been changed from bad to excellent, as for instance, by the construc- tion and proper operation of adequate purification works, has shown that for every person thus saved from death from typhoid fever, approximately three other persons are saved from death from other causes, many of which have probably never been thought to have any direct connection with, or to be especially effected or influenced by the quality of the public water supply. This numerical statement of the reduction in death rate more or less directly due to improved water supplies has recently become known as the Hazen Theorem, because Mr. Allen Hazen in 1903- 05 was the first to announce in definite terms this interesting and most encouraging phenomenon. Even such unexpected diseases as tuberculosis, pneumonia, bronchitis, and a series of disturbances causing undue mortality among infants seems to be decidedly affected by such changes in the quality of the water supply. From general principles it is to be inferred that the drinking of a polluted and insanitary water supply must surely tend to lower the vital resistance. On the other hand, an im- proved water supply must mean a real improvement in the general health tone of the community, a real uplift and rein- forcement, rather than an impairment of the vital resistance of the consumer of such supplies.” While all the established facts point to the vital necessity for clean and wholesome water supply, what are we doing and what can we do to insure such a supply to every community in the land? The use of extremely minute quantities of chloride of lime, 14 Chloride of Lime in Sanitation. has offered a very practical and simple solution of the sanitary troubles of nearly every city water supply. The most astonish- ing part of all this is that the true import of these facts has only been realized within the last four years. As a practical process it dates from 1908, when Mr. G. A. Johnson of New York City was called in to remedy some serious trouble in the water purification at the Chicago Stock Yards. The filtered water of Bubbly Creek'** contains a large amount of sewage and it had been purified by a process of filtra- tion in conjunction with copper sulphate, but it was the com- plaint of the large stock shippers that animals drinking this filtered water made less gain in weight than when city water was supplied them. Under pressure of a lawsuit brought by the City of Chicago against the Union Stock Yards Company, the con- tractors for the filter plant were, however, enabled to fulfill their guarantees by Mr. Johnson substituting chloride of lime for the copper sulphate. The treatment raised the quality of the sew- age-laden water from the Creek far above that of the Chicago city water, as was shown in its low percentage of cases where B. coli were found. B. coli found Bubbly Creek, treated..............2.ceeeeeee 0.84% of cases Chicago City water.... 12.8% of cases The hypochlorite was added 7} hours before filtration; the addition after filtration did not give as satisfactory results. The amount of chloride of lime added was forty-five pounds per 1,000,000 gallons. Thus a new epoch in the annals of water purification dates from Mr. Johnson’s success at Chicago. Destroying bacteria in water and sewage by chloride of lime had been the subject of active investigations for some twenty years before, but with the information fragmentary and in- definite in character, the process had not gained credence. Mr. Johnson gave to the problem (made particularly difficult through large variations in percentage of sewage) its definite solution. The benefits from ‘this simple expedient have been felt all through the land, where in more than one hundred cities it has Chloride of Lime for Water Purification. 15 been called in as a prompt and powerful ally in fighting typhoid fever. It has shown itself to fit in with every situation and condition of water supply; with waters from springs or from natural reservoirs, as supplied to New York and other cities; with impounded waters; with the polluted waters from the Mis- sissippi, St. Lawrence River, or Missouri, Ohio and many other sources; where typhoid has been allayed in cities, like Omaha, Cincinnati, St. Louis, Minneapolis, Montreal, as well as in cities adjacent to the Great Lakes, as Cleveland, Erie, Chicago, Mil- waukee, where contamination by sewage or chance pollution from shipping and annual winter typhoids had been the rule. It has been codrdinated with every existent process of water purification, as plain sedimentation, sedimentation after coagu- lation, slow sand filtration, mechanical filtration, single and double filtration. The value of chloride of lime for straightening out difficulties becomes manifest in a situation like the following, depicted in the testimony of Mr. Calvin W. Hendrick, chairman National Association for Prevention of Pollution of Rivers and Water- ways, in the hearings given recently before the Senate Com- mittee on the Owen bill, purporting the creation of a Federal Department of Health: “Cincinnati takes her drinking water from the Ohio river above the city, discharging her sewage into the same river below for others to drink down the river. “The cities of Newport and Covington, Ky., use the same river for the discharge